Don't hesitate to try to diy. Blow it out with an air compressor and run a lightly oiled rag over it and it will run. The trigger group comes out easily by popping out the two pins in the action. Blow out the firing group, lightly oil the action, no oil on the firing group and put it back in. Make sure to take off the foreend and lightly oil the magazine tube after blowing it out. If the mag tube is lightly oiled and cleaned every hundred rounds or so the rest of the gun will run. I use Rem oil on my 1100's, it is a very light oil and perfect for the 1100 in all weather conditions.
Don't worry about the springs unless there is a problem. I am running a 40 year old, or so, 1100 with the original springs. I don't know how many rounds those spring have on it, probably thousands.
The only problem you might have is that the gun wasn't broken in, it may take a couple boxes to get everything "married" but on those old 1100's they were fit very nicely and you likely won't have any problems.